Thermoplastic elastomeric (elastoplastic) compositions comprising blends of cured rubber and polyolefin resin are known, (Gessler et al, U.S. Pat. No. 3,037,954; Coran et al, U.S. Pat. No. 4,104,210; and Campbell et al, Natural Rubber Technology, Volume 9, Part 2, 1978, pages 21 through 31). Gessler indicated that conventional rubber curatives were suitable for preparing blends containing high proportions of polypropylene. Coran recommended curative systems comprising bis-maleimide and, also, particularly recommended efficient or semi-efficient sulfur curative systems comprising high accelerator/sulfur ratios for preparing blends containing high proportions of rubber. Campbell et al described the preparation of rubber-polyolefin resin blends using organic peroxide curatives. The aforesaid blends exhibit limited durability as measured by true stress at break or limited elastic recovery (resistance to set). Higher strength compositions could be obtained by increasing the relative proportion of polyolefin resin, but the gain in strength was obtained at the expense of elastic recovery. Increasing the relative proportion of rubber improved elastic recovery, but it also decreased ultimate elongation, tensile strength and true stress at break.